Not only did I/I did

[Over the top]

Which one is correct
Not only did I read it, but I helped write it
Not only I did read it, but I helped write it
Not only I read it, but I helped write it

Thank you

[buggles]

Which one is correct
Not only did I read it, but I helped write it.
Not only I did read it, but I helped write it.
Not only I read it, but I helped write it.

Thank you

Not only did I read it, but I helped to write it.

Your first sentence is OK, but it sounds better with the "to".

buggles (not a teacher)